Definition
A loss of the ability to transmit, receive, or both, between an aircraft and air traffic control (ATC) by radio. Pilots operating under instrument flight rules (IFR) who experience this failure are required to follow specific lost communication procedures regarding route, altitude, and clearance limit, and to squawk transponder code 7600 to alert ATC.
Plain English
When the radio between you and air traffic control stops working — either you can't hear them, they can't hear you, or both — and you can't talk to each other anymore. There are set rules that tell you what route and altitude to fly when this happens, so ATC can predict where you'll go.
Context Anchor
Seen in AIM lost-radio procedures, controlled airspace operations, instrument clearances, and towered airport operations.
Why Pilots Care
Triggers standardized lost-communications procedures that protect separation and let the flight continue safely to its destination.
Intuition Check
Do not assume this means only that the radio is completely dead. If the needed back-and-forth radio contact cannot be made, the situation is treated as a two-way radio communications failure.
Example Sentence 1
After losing both radios in IMC, the pilot squawked 7600 and continued on the last assigned route in accordance with two-way radio communications failure procedures.
Example Sentence 2
The student pilot practiced the two-way radio communications failure procedure by flying the published route without any ATC calls.